Drafting instrument



Dec. 7, 1937. a T ERICKSQN L 2,101,365

DRAFT ING I NS TRUMENT Filed April 5, 1957 2' Sheets-Sheet 1 INVENTOQ; 1.11 EmcKsoN Rnotzryev Dec. 7, 1937. T. T. ERICKSON DRAFTING INSTRUMENT Filed April 5, 1937 2 Sheets-Sheet 2 Imam-oz,

'T'. 1. Ezlcl ban Patented Dec. 7, 1337 UNITED STATES PATENT OFFICE DRAFTING INSTRUMENT Tony T. Erickson, South Hibbing, Minn.

Application April 5, 1937, Serial No. 134,961

1 Claim.

My invention relates to improvements in drafting instruments and the main object is to provide an instrument in a simple and convenient form which combines the functions of a scale, rule,

5 triangle, square and protractor for draftsrnens use.

Another object is to provide an instrument of this kind including a base or horizontal bar which in use on the drawing board would be placed on 10 the usual T square, a graduated protractor disk rotatably mounted on the base bar and with a lock for locking the disk at any point around an arc of ninety degrees, and a scale bar secured to the protractor disk with a pair of arms ex- 15 tended at right angles and graduated in any desired scales.

With these and other objects in view the invention resides in the novel construction and arrangement of parts as hereinafter fully set forth 20 and claimed, reference being had to the accompanying drawings as showing a preferred embodiment of my invention for purposes of exemplification.

In the drawings:

25 Figure 1 is a plan view illustrating the use of my instrument on a drawing board and with a T square.

Figure 2 is an enlarged plan view, partially broken away of the instrument alone.

3 Figure 3 is a cross section along the line 3-3 in Figure 2.

Figure 4 is a fragmental section along the line 4-4 in Figure 2.

Figure 5 is a cross section along the line 5-5 35 in Figure 2.

Figure 6 is a fragmental enlarged plan view showing a section of the protractor disk and its look.

In carrying out my invention I provide first 40 a protractor base bar ll) of elongated flat shape with straight upper and lower parallel margins II and I2. The terms upper and lower as used in this description are understood to refer to the positions of the parts as they are used on 45 a drawing board though obviously in other uses as will be pointed out these positions may be changed.

A circular fiat protractor disk I3 is provided and is rotatably and detachably mounted on the face of the bar I by a thumb screw l4 passed through a centrally located aperture l in the disk and threaded at l6 into the bar. The protractor disk |3 may thus rotate freely on the base bar I0 about the pivotal connection afforded by the thumb screw l4. Opposite quadrants of 55 the disk I3 are graduated in degrees from 0 to 90 as shown and in such manner that at normal position of the disk (Figure 2) 0 will occur in line with the axis of the bar H). An index I! is secured by a screw Hi to the bar 10 at one side of the disk l3 so that the indicator V [9 will r register with "0 on one scale as referred to by the numeral 20. At a diametrically opposite point a lock for the protractor is provided, the same including a housing 2| secured by screws 22 to the bar in and a latch plunger 23 slidably mount- 10 ed in the housing. This plunger 23 is normally urged toward the margin of the disk i3 by an expansion coil spring 24 which is coiled around a reduced shank 25 of the plunger and braced against the outer end of the housing 2| as shown. The said shank 25 extends slidably through an aperture 23 in said outer end of the housing. The plunger 23 may however be drawn back or away from the disk |3 by means of a knob 21 affixed to the plunger and extended therefrom through a slot 28 in the housing as shown. The disk H! has a series of notches 29 cut in its periphery around one quadrant and one notch is located in exact alignment with each degree marking of the scale 30 and the nose of the plunger 23 is pointed as shown at 3| to enter any one of these notches and so lock the disk I3 against rotation until the plunger is released by pulling backward on the knob 21. In this manner the disk I3 may be locked in any position around an arc of ninety degrees and the position read either at the index I! or at the plunger 23. The upper side of the housing 2| extends over the adjacent margin of the disk l3 but is cut back as at 32 to expose the pointed end of the plunger and to serve as an index at this point.

A scale and square structure shown generally at 33 is provided and comprises a pair of arms 34 and 35 joined and extended at right angles. The disk l3 then has a portion intermediate the scales 2!] and 30 out or notched out as shown at 36 and the right angled margins 31 of this notch are reinforced as at 38 so that the corner 39 of the scale 33 will fit nicely thereunder. Thumbscrews 40 are passed through apertures 4! in these margins 37 and are screwed at 42 into the corner of the scale securing the scale to the protractor disk. The position of the parts as thus mounted is such that with the protractor disk l3 turned to register at 0 on the scales one arm 34 of the scale will lie flush along the upper margin ll of the base bar H! while the other arm 35 extends upwardly at right angles therefrom. The inner margins of the arms 34 and 35 are beveled off and graduated as shown at 43 while the arms are each longitudinally slotted as at 44 forming another pair of margins which are beveled and graduated as shown at 45. The graduations on all these margins may be of any style desired and suitable to the use of the instrument.

In use on a drawing board B the base bar III is placed on the upper edge of the T square blade T thus locating the upper edge of the bar in a horizontal line relative to the board. By then drawing along either of the scale arms 34 and 35 horizontal or vertical lines may be drawn and by releasing the plunger 23 and rotating the pro-.

tractor disk l3 lines may be drawn at right angles at any angle to the vertical or horizontal. The disk l3 being placed atop the bar I is in position to overlie the T square as shown in Figure 1 and so will not interfere with the proper positioning of the instrument on the board. By releasing the thumbsorews 40 the scale 33 may be removed and used .as a square or measure. Further uses of the device will be apparent and it will be evident that by my invention I have eliminated the necessity for separate scales, squares, triangles and protractors as now used by draftsmen and others.

While I have herein set forth a certain preferred embodiment of my invention it is understood that I may vary from the same in minor structural details, so as best to provide a practical device for the purposes intended, not departing from the spirit of the invention and within the scope of the appended claim.

I claim:

In a device of the kind described, a flat protractor base bar, a protractor disk of substantially greater diameter than the width of the base bar rotatably mounted upon the base bar, the disk being demarked upon its predetermined upper face with a pair of diametrically oppositely positioned quadrants doubly calibrated and with the calibrations reversely numbered from zero to ninety degrees from right to left and from left to right, there being a right angled portion cut out of the disk through its periphery at one side immediately between the pair of quadrants demarked as aforesaid and at one end of the space intervening thereinbetween, the sides of the right angled cut out being extended in spaced and parallel relation to a right angle having its vertex coinciding with the center of the point of rotation of the protractor disk, and a flat, right angled scale and square element mounted at its corner underneath the margins of the right angled cut of the disk and in exact registry therewith and detachably secured thereto by screws passed down through said margins into the element, and means for releasably locking the protractordisk in any set position of rotation.

TONY T. ERICKSON. 

